[General Discussion] Hardest game(s) you've ever played

I will have to say the Adventures of Cookie and Cream. Definitely not the kids game that it looks to be. First off, both you and your partner have to be good, and although the levels start out easy, the difficulty quickly escalates. Second, you need a good sense of teamwork, so if you don't work well with others and have patience, then you're screwed no matter how good you are by yourself. Third, the penalty for getting hit/falling is heavy, with a whopping 20 seconds deducted from your time each time you make a mistake. Some puzzles are terribly confusing as well with strange uses for items that wouldn't normally used in such ways. You'll need a good eye to spot these things.

Jam it back in, in the dark.